1. Field of the Invention
This invention relates to an endosseous implant for prosthesis embedded in the bone tissue of a living body and more particularly to an endosseous implant for dental prosthesis or orthopedic surgery and having a mesh pore structure adapted for any implant used in the form of a platelike, tubular or columnar body.
2. Prior Art
Conventionally well known is a ceramic implant such as described in U.S. Pat. No. 4,259,072 in the form of a prosthetic member for a living body and such an implant as disclosed in Japanese Patent Laid Open Publication No. 10163/1982 wherein metal beads such as titanium, zirconium are sintered for use in an aritificial tooth root.
But in the former ceramic implant described above, the opening size of the pore, shape of netlike root, pore size and pore distribution in the ceramic implant, depend upon the kind of foaming agent making ceramics porous or upon sintering conditions so that it is difficult to artificially control the desired shape, size and distribution of the pores. On the other hand, since the latter implant has a core metal around which the above mentioned metal beads are sintered, is composed of composite bodies of core metal and metal grains sintered therearound, the implant necessarily has a limit on the minimal value of the diameter of a column. Supposing that the core metal is for example 2 mm in diameter and sintering materials are sintered therearound, the diameter of the column eventually measures at least more than 4 mm, with the result that the columnar sintered metal grain body can be used only in the alveolar bone having a large width and makes difficult its application to the case wherein the width of the alveolar bone is relatively small. The two types of implant mentioned above are not free from the problems described above.
Such being the case, the present inventors previously provided an implant (Japanese Patent Application No. 264994/1985) having a plurality of straight tubular cylindrical channels permitting the ingrowth and penetration of bone tissue, osteoid tissue and fibrous tissues into a metal plate as of titanium and zirconim, and also provided an implant of a platelike body of sintered metal beads and a frame integrally bound around the body, into which platelike body the ingrowth and penetration of the bone tissues is permitted. Each of the previous implants thus provided contributed greatly toward increased adaptability of the endosseous implant by enabling an architectural structure of bone made of both hard and soft tissues to hold the implant biodynamically in the interface between the implant and the bone tissue.
The inventors, after further research, have found that the former implant constructed by forming tubular cylindrical channels in the metal plate leaves a problem to be solved in making pores of various diameters and that the latter implant produced by sintering the beads into a plate form also not only makes it comparatively cumbersome in its manufacturing step to form desired pores with desired geographical distribution but also needs additional beads for making up for fissured clearance produced between a frame and the beads by contraction of the metal beads after the beads have been sintered. The implants thus have the problems yet to be solved.